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Pineapple wilt disease (380) Print Fact Sheet

Common Name

Pineapple wilt

Scientific Name

Mealybug wilt of pineapple

Distribution

Worldwide; in all the major pineapple growing areas: Asia, Africa, South, North and Central America, the Caribbean, Oceania. In has been recorded from Australia, Cook Islands, Fiji. Plants from American Samoa and Samoa found to be infected for two pineapple mealybug wilt-associated viruses (PMWaVs) when maintained in the USDA-ARS National Clonal Germplasm Repository, Hilo, Hawaii.

Hosts

Pineapple and Pseudoananus. The latter is commonly called the false pineapple, not grown commercially (https://commons.wikimedia.org/wiki/File:Pseudoananas_sagenarius_(8400437895).jpg).

Symptoms & Life Cycle

The disease causes a reddening (later pink), severe tip dieback, downward curling and wilting of the leaves; there is also a collapse of the roots (Photos 1-4). Recovery can occur, but fruits are small.
 
Pineapple wilt appears to be influenced by age of the plants: young plants develop symptoms in 2-3 months; older plants take up to a year.
 
The disease is associated with the mealybugs, Dysmicoccus brevipes (pink mealybug) and Dysmicoccus neobrevipes (grey mealybug) (see Fact Sheet no. 282). These mealybugs feed on pineapples, acquire Pineapple mealybug wilt-associated virus(es) and then pass the viruses to other plants. Both adults and young do this, but young mealybugs, known as 'crawlers', are the more important. The viruses are acquired after feeding on infected plants for about 72 hours, and the mealybugs remain infective for up to 3 days.
 
Research into the cause of pineapple wilt shows that one of the viruses, known as PMWaV-2, is the more important, but the presence of feeding mealybugs is also necessary for symptoms to develop. Another, related virus, PMWaV-1, is common, but with or without mealybug feeding its presence does not lead to pineapple wilt, although it may cause yield reduction.
 
Mealybugs from outside the field that are initially free from infection become established on PMWaV-2 infected plants; these plants develop the wilt disease and secondary spread occurs as the infected mealybugs move to PMWaV-free plants.
 
Spread of the disease over short distances is by ants and wind. Ants tend the mealybugs collecting honeydew for food and also move the ants from plant to plant. Honeydew is excreted by the mealybugs as they feed on plant sap. The wind carries crawlers between plants and plantations. Long distance spread occurs via all life stages of the mealybugs in consignments of fruit and propagating material traded nationally and internationally. 

Impact

Pineapple wilt occurs worldwide, is important, although often variable in plantations. This is because the disease depends on the presence of the virus(es), the number of mealybugs present, the length of time they feed, and the presence of ants. Trials in Hawaii showed that if pineapple wilt occurs during the first 3 months of the plant crop, average fruit weight is reduced by 55% compared to plants that remain virus free.

Detection & Inspection

Look for early symptoms - reddening of leaves about halfway up the plant. Look for a change of colour from red to pink, a downward roll of the leaves and dieback of the tip as the leaves collapse. Look for Dysmicoccus mealybugs which spread the wilt disease.

Management

Management of pineapple wilt is difficult. It depends on at least four factors: i) clean (virus-free) planting material; ii) removal of weeds; iii) mealybug control; and iv) plant density.

NATURAL ENEMIES
There are a large number of predators and parasitoids of Dysmicoccus brevipes, including ladybird beetles, particularly Cryptolaemus species (see Fact Sheet no. 395), and wasps (encyrtids). In many countries, biological control is effective when ants (Pheidole, Iridomyrmex and Solenopsis) are controlled (see Fact Sheet nos. 361, 362&363).

QUARANTINE
Importation of pineapple plants for planting from countries where pineapple wilt occurs should not be permitted unless they are kept under observation in closed post-entry quarantine and tested for pineapple viruses (ampeloviruses and badnaviruses, in the Closteroviridae and Caulimoviridae families, respectively). For fresh fruit, an import risk analysis should be considered where countries are vulnerable to this serious disease, its mealybug vectors and associated ants. Conditions invariably require fresh pineapples to be de-crowned, from registered commercial plantations, fumigated pre-shipment, and inspected on arrival.   CULTURAL CONTROL
The control measures recommended below are for the control of the mealybug, and also for the control of Pineapple mealybug wilt-associated virus(es) that they are thought to spread.

Before planting:

During growth:

After harvest:

CHEMICAL CONTROL


AUTHOR Grahame Jackson 
Information from Sether DM et al. (2001) Differentiation, distribution, and elimination of two different Pineapple mealybug wilt-associated viruses found in pineapple. Plant Disease 85:856-864. (https://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS.2001.85.8.856); and J Hu (2002) Detection, Characterization, and Management of Pineapple Mealybug Wilt-Associated Viruses. (http://www2.hawaii.edu/~johnhu/pineapple.pdf); and Subere C et al. (2009) Vector transmission of Pineapple mealybug wilt associated virus-2 by Dymiococcus neobrevipes and Peudococcus lngispinus in Hawaii. Phytopathology 99: S125; and from Subere CVQ et al. (2011) Transmission characteristics of pineapple mealybug wilt associated virus-2 by the grey pineapple mealybugs Dysmicoccus neobrevipes in Hawaii. Proceedings 7th International Pineapple Symposium. Eds.: Abdullah H et al. Acta Hort. 902, ISHS. (https://www-actahort-org.ezproxy.library.uq.edu.au/members/showpdf?session=12083). Photos 1&2 United States National Collection of Scale Insects Photographs, USDA Agriculture Research Service, Bugwood.org. Photos 3&4 United States National Collection of Scale Insects Photographs, USDA Agricultural Research Service, Bugwood.org.

Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/185: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland and the Secretariat of the Pacific Community.



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